Runaway BHP ore train left a twisted wreck after derailment stopped it reaching port town

Rail safety investigators have arrived at the site of a deliberate train derailment in Western Australia's Pilbara region, a day after a runaway train brought iron ore miner BHP's rail network to a halt.

The fully-laden train, pulling 268 wagons of iron ore, was travelling from Newman to Port Hedland when the driver got out to inspect a wagon near Hester siding at 4:40am on Monday.

While the driver was out of the cabin, the train took off, travelling more than 90 kilometres in 50 minutes.

Out-of-control train 'very concerning': PremierWA Premier Mark McGowan said while he had not been briefed on the incident, it was clear "extraordinary measures" had been required.

"Obviously it would have been very concerning for everyone involved — BHP and the workforce, and the people of Port Hedland — that a train was travelling down the track without a driver and obviously out of control," Mr McGowan said.

"I'm sure that there'll be a full review undertaken by BHP, and I'll consult about what role the state might have in that."

In a statement, BHP said about 1.5 kilometres of track was damaged, and the recovery process would take about one week.

"We are working with the appropriate authorities to investigate the situation," the company said.

In the meantime, train operations across BHP's network have been suspended.

Data recorder may hold answersBased on the distance travelled, the runaway train reached an average speed of about 110 kilometres per hour.

Rail Safety Consulting Australia owner Phillip Barker said it was unclear what had happened to make the train take off, but suggested it may have involved the configuration or isolation of the brake system.